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PC Sizing
Pool Surface Area
As the square footage of the pool increases, the
evaporation rate will increase proportionally. This is due to the
increase in size of the surface water / air contact area. The
depth, shape, and total volume of the pool do not affect the
evaporation rate.
PC Unit Sizing
The amount of evaporation occurring in a residential pool
application of a given size is governed mainly by the tempera-
tures at which the air and water are maintained. It is common
practice to keep the air temperature 2°F above the pool water
temperature. The lower the air temperature is in comparison to
the water temperature, the higher the evaporation rate will be.
The evaporation rate of the pool increases when the following
occur:
1) Pool water temperature increases
2) Activity level / wet floor area increases
3) Airflow across pool surface increases
4) Room air temperature decreases
5) Room relative humidity level decreases
1) Pool water temperature: The temperature of the pool
water in relation to the air temperature is one of the most
important factors in determining overall evaporation rate from
the pool. As the room air temperature decreases in relation
to the pool water, the evaporation rate will increase
dramatically. The normal pool water temperature range for
private pool use is from 78°F to 82°F. The air temperature
should be kept 1° to 2°F above the water temperature for the
most economical operation of the pool conditioner.
2) Activity level / wet floor area: During pool use, water will
be drawn out of the pool by the action of swimmers leaving
and re-entering the pool during normal activities. This water
will accumulate on the floor surrounding the pool and will
contribute to the overall surface exposed to the air for
evaporation purposes. If the pool floor is heated then the
evaporation rate will exceed that of the pool itself and this
extra wetted area should be considered in sizing the pool
conditioner.
TABLE 3 - Step by Step Pool Evaporation Rate Calculation
Step
1
Select pool water temperature*
2
Select pool room air temperature*
3
Select Non-Active Humidity Level (50 or 60%)
4
Select the number of active hours
5
Calculate the number of non-active hours = 24 - Ha
6
Lookup the active Evaporation Rate Factor from
7
Lookup the non-active Evaporation Rate Factor from
8
Select the activity factor (see
9
Calculate the Average Evaporation Rate Factor = [(Ha x ERFa x AF) + (Hna x ERFna x 0.5)] / 24 ERFavg
10
Select Pool Surface Area
11
Calculate Pool Evaporation Rate = Ap * ERFavg --> match to Moisture Removal in
*It is recommended that the air temperature be 2°F above the pool water temperature. The lower the air temperature in comparison to
the water temperature, the higher the evaporation rate. Typical residential values are Tp = 80°F (27°C) and Ta = 82°F (28°C).
ISSUE 03: 1-Oct-2021
Action
TABLE 8
TABLE 7
TABLE
6)
Page 8
TABLE 4 - PC Typical Sizing (60 Hz)
Pool Sur-
Airflow
face Area
Model
cfm (L/s)
PC-45
1200 (570)
PC-55
1500 (710)
PC-65
1900 (900)
PC-75
2100 (990)
1200 (110)
PC-80
2400 (1130)
1350 (130)
*Residential application with Tp=80°F and Ta=82°F
EWT=80°F and EAT=82°F
TABLE 5 - PC Typical Sizing (50 Hz)
Pool Sur-
Airflow
face Area
Model
cfm (L/s)
PC-45
1200 (570)
PC-55
1500 (710)
PC-65
1900 (900)
PC-75
2100 (990)
PC-80
2400 (1130)
1100 (102)
*Residential application with Tp=80°F and Ta=82°F
EWT=80°F and EAT=82°F
TABLE 6 – Activity Factor (AF)
AF
0.5
residential
0.65 therapy, aquafit, elderly swim, fitness club, condominium
0.8
hotel
0.8
school
1.0
public pool, spa, or whirlpool
or
8
(50 or 60% from Step 3).
TABLE 4
Moisture
Moisture
Removal
Removal
@50%RH
@60%RH
2
2
ft
(m
)
lb(kg)/hr
600 (56)
14 (6.4)
800 (74)
19 (8.6)
1050 (98)
24 (11)
28 (13)
32 (14)
Moisture
Moisture
Removal
Removal
@50%RH
@60%RH
2
2
ft
(m
)
lb(kg)/hr
500 (46)
13 (5.9)
700 (65)
16 (7.3)
900 (84)
20 (9.0)
1000 (93)
23 (11)
26 (12)
Application
Variable Example
Tp
80
Ta
82
RHna
50
Ha
2
Hna
22
ERFa
0.036
ERFna
0.048
AF
0.5
0.0235
Ap
800
or
5
ERp
18.8
002291MAN-03
lb(kg)/hr
18 (8.2)
23 (10)
30 (14)
33 (15)
38 (17)
lb(kg)/hr
15 (6.8)
19 (8.6)
25 (11)
28 (13)
32 (14)
Unit
°F
°F
%
hours
hours
2
lb/hr/ft
2
lb/hr/ft
2
lb/hr/ft
2
ft
lb/hr
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